1. Field of the Invention
The present invention relates to a solid polymer electrolyte membrane, a method for manufacturing the same, and a fuel cell that includes the solid polymer electrolyte membrane.
2. Description of the Background
Ionic conductors through which ions can flow have been widely used as electrochemical devices such as fuel cells, electrochemical sensors, and the like.
Some types of fuel cells require proton conductors that can provide good proton conductivity for a long period of time at an operation temperature of about 100° C. to about 300° C. at no humidity or a relative humidity of 50% or less. A solid polymer fuel cell that uses an electrolyte membrane formed of a perfluorocarbonsulfonic acid does not have sufficiently high energy generation efficiency at an operation temperature of about 100° C. to about 300° C. with a relative humidity of 50% or less.
A fuel cell that uses an electrolyte membrane that includes a proton conductivity donor is disclosed in Japanese Patent Laid-Open Publication No. 2001-035509. A fuel cell that uses a silica-dispersed membrane is disclosed in Japanese Patent Laid-open Publication No. Hei 06-111827. A fuel cell that uses an inorganic-organic composite membrane is disclosed in Japanese Patent Laid-open Publication No. 2000-090946. A fuel cell that uses a phosphoric acid-doped graft membrane is disclosed in Japanese Patent Laid-open Publication No. 2001 -213978. A fuel cell that uses an ionic liquid composite membrane is disclosed in Japanese Patent Laid-open n Publication Nos. 2001-167629 and 2003-123791.
In addition, U.S. Patent No. 5,525,436 discloses a solid polymer electrolyte membrane that includes polybenzimidazole doped with a strong acid such as phosphoric acid.
However, the fuel cells disclosed in Japanese Patent Laid-open Publication Nos. 2001-035509, 2000-090946, and 2001-213978, and Japanese Patent Laid-open Publication No. Hei 06-111827 cannot stably generate energy for a long period of time even at an operation temperature of about 100° C. to about 300° C. at no humidity or a relative humidity of 50% or less.
In addition, because phosphoric acid fuel cells, solid oxide fuel cells, and molten salt fuel cells have a very high operation temperature of 300° C., the components of the fuel cells have poor long-term stability.
U.S. Patent No. 5,525,436 describes a solid polymer fuel cell that exhibits comparatively high energy generation at high temperatures of up to about 200° C. However, the energy generation efficiency of the fuel cell cannot be stably maintained over a long period of time.
Thus, there exists a need for a fuel cell with improved energy generation performance, system efficiency, and long-term durability of the fuel cell components to stably maintain high energy generation efficiency over a long time period at an operation temperature of about 100° C. to about 300° C. at no humidity or a relative humidity of about 50% or less.